I. Field of the Invention
This invention relates generally to a sleeping bed sleeping bed assembly for use in motor vehicles, such as over-the-road tractor/trailer rigs and recreational vehicles, and more particularly to apparatus for isolating the bed from effects of shock and vibration to which the vehicle is subjected when traveling.
II. Discussion of the Prior Art
Over-the-road truckers often drive in teams in which one person drives while the other rests. Modern semi-tractors include a sleeping compartment disposed behind the driver and passenger seats, and this sleeping compartment is equipped with a bed for accommodating a recumbent individual. Likewise, recreational vehicles and motor homes often include one or more beds. With such motor vehicles, and especially semi-tractors which tend to have a stiff suspension system, shocks and vibrations caused by the vehicle hitting irregularities in the pavement surface, negotiating turns, accelerating and decelerating can be transferred to the individual trying to rest and thus disturbing his/her sleep. When it is considered that serious highway accidents have been attributable to drivers who are not well rested, it is important that they be allowed to sleep soundly while another driver operates the vehicle so that transport time will not be unduly increased.
Others have addressed the problem of attempting to properly isolate a sleeping bed in a motor vehicle from shock and vibration forces. In the Lefler et al. U.S. Pat. No. 4,196,483, there is described a bed arrangement comprising a mattress support frame supported over a base and secured for vertical movement through the use of an air cylinder and valve combination which functions as an air spring. The valve operates such that air is introduced into the air spring when a force tends to draw the movable frame toward the stationary frame and will exhaust air from the air spring when the two frames tend to move apart. No provision is made in the Lefler et al. bed arrangement to accommodate shock and vibration forces directed other than vertically. That is to say, no attempt is made to counteract breaking and acceleration forces or side-to-side sway of the vehicle.
The Vogel et al. U.S. Pat. No. 4,497,078 also is concerned with isolating a sleeper from shock and vibration in a vehicle-mounted bed. It, like the Lefler et al. device, incorporates air bags disposed at the foot end and head end of the bed and operating along a vertical axis to cushion up-and-down movement of a movable frame relative to a truck-mounted stationary frame. Unlike the device of the Lefler et al. patent however, the Vogel et al. system also incorporates an air spring disposed in a horizontal plane and operatively coupled to dampen out shock and vibration forces directed horizontally in the fore and aft direction. Vogel et al. further recognizes the problem with air bags in that they may violently overshoot and "launch" the sleeper into the air, especially when a sudden impact occurs in the vertical direction, such as when the truck encounters a pothole or similar flaw in the road surface. By providing an accumulator with each of the air bags, such overshoot and continued oscillation is removed.
The present invention is deemed to be an improvement over the prior art as represented by the Lefler et al. and Vogel et al. patents in that it provides resistance to inertial forces acting in all three axes, i.e., vertically, fore & aft and side-to-side. Moreover, the system of the present invention is greatly simplified in that only two air bags are required, one at the head of the bed and one at its foot, both operating along a vertical axis to resist the tendency of the moveable frame and mattress to move up-and-down. Furthermore, by incorporating a hydraulic cylinder as a snubber connected in parallel with the air bags, any tendency for the moveable frame to overshoot in the upward direction following a sudden compression is obviated. In the present invention, no air bags and associated valve mechanisms are utilized for resisting fore-to-aft motion and side-to-side motion. Instead, tension springs are effectively used to couple the moveable frame to the stationary frame and then air cylinders, functioning as dampeners, are used to suppress any tendency for the moveable frame to oscillate following the application of horizontally-directed forces to the bed and its occupant.